1. Field of the Invention
This invention relates to a high-frequency line structure on a resin substrate and a method of manufacturing the same, the high-frequency line structure being adapted for reducing the propagation loss of a high frequency signal.
2. Description of the Related Art
In wiring substrates for use in mobile communications devices which use radio signals, such as microwaves or millimeter waves, whose radio wavelengths range from approximately one meter down to approximately one millimeter, a high-frequency line structure for propagating a radio signal is provided (for example, see FIG. 1). In the following, a radio signal that is propagated on a high-frequency line structure will be called a high frequency signal.
FIG. 1 is a perspective view illustrating the composition of a high-frequency line structure 200 on a resin substrate according to the related art. As illustrated in FIG. 1, the high-frequency line structure 200 according to the related art is a microstrip type high-frequency transmission line. The high-frequency line structure 200 includes a dielectric layer 201, a signal wiring 202 disposed on a top surface 201A of the dielectric layer 201 to propagate a high frequency signal, and a ground layer 203 disposed to cover a bottom surface 201B of the dielectric layer 201. For example, Japanese Laid-Open patent publication No. 2002-280748 discloses a high-frequency line structure of this type.
The high-frequency line structure 200 according to the related art has a problem that the propagation loss of the high frequency signal will be increased if the length of the signal wiring 202 is increased.
Electromagnetic waves or magnetic fields which are the components of the high frequency signal are leaked out from the signal wiring 202 into the air, and the high-frequency line structure 200 according to the related art has a problem that the propagation loss of the high frequency signal will be further increased.